(a) Field of the Invention
The present invention relates to a novel process for the preparation of 4,4'-biphenol. It also relates to a precursor of 4,4'-biphenol, that is, 4,4-bis(4-hydroxyphenyl)cyclohexanol of the formula (I): ##STR1## and a process for preparing the precursor.
(b) Description of the Prior Art
4,4'-Biphenol is useful as a stabilizer and a dyestuff intermediate as well as a material for the resin such as polyester, polyepoxide, polyurethane, polycarbonate and the like. In particular, it has recently attracted attention as a material for high-temperature resistant resin.
Various processes have so far been proposed for the preparation of 4,4'-biphenol. A preparation process by the diazo decomposition of benzidine has been known for a long time [Chemische Berichte, 22, 335]. Another preparing process by the alkali fusion of sodium 4,4-bisphenyldisulfonate has afterward been known [U.S. Pat. No. 2,368,361 (1942)]. In recent years a process for obtaining biphenol by the dealkylation of tetra-tert-butylphenol derived from 2,6-di-tert-butylphenol has been widely investigated and many patents have been published [Journal of Organic Chemistry, 34, 1160 (1969) etc.]. In addition, also known are processes for obtaining biphenol by the dehalogenation and dimerization of dihalogenated phenols (Japanese Patent Laid Open No. 53631/1981) and by the alkali treatment of halogenated biphenyl (Japanese Patent Laid Open No. 22347/1979). In addition, various other preparation processes have been proposed. Above-mentioned conventional processes, however, have drawbacks such as harmfulness to health or expensiveness of raw materials, problems on waste disposal, need for severe process conditions, low yield and so on.